The specific activation of T lymphocytes which govern the immune response occurs via stimulation of the T Cell Antigen Receptor. This is a multichain and multimorphic receptor existing as either a seven or nine chain transmembrane complex. In most mature T cells, the ligand specificity is imparted by two chains, alpha and beta, which exist as a heterodimer. In all T cells these chains are non-covalently linked to four other membrane proteins, Gamma, Delta, Epsilon and Gata homodimer, as a seven-chain complex. In all T cells studied, we have found that 10% of the cell receptors possess a Gata-p21 heterodimer in addition to or instead of the Gata homodimer. The structure, initially described in murine T cells with absent and/or abnormal subunits are studied to illuminate the structural and functional roles of individual receptor components. The cycling dynamics of the cell surface T cell receptor have been studied and kinase- mediated perturbations examined. The process of biosynthesis, maturation, assembly, degradation and intracellular routing of receptor components are studied both in T cells and in fibroblasts expressing individual genes or sets of genes encoding these subunits. Models for the relationship between assembly and intracellular sorting have been developed. Previously unanticipated routes of intracellular degradation (and sorting) have been suggested by these studies. A new protein has been identified which may play a specific role in the targetting and/or assembly of newly synthesized receptor chains.